Position signaling devices for sewing machine driving unit

ABSTRACT

A direct drive unit for a sewing machine applied on the sewing machine frame co-axially of the sewing machine main shaft including a device for producing signals responsive to discrete positions of the sewing machine main shaft. The position signaling device is capable of indicating a plurality of different angular positions of the sewing machine main shaft, which positions may be selected simply by turning frictionally restrained arms accessibly located on the free extremity of the drive unit into the angular positions for which signals are desired.

United States Patent Kleinschmidt et al.

[54] POSITION SIGNALING DEVICES FOR SEWING MACHINE DRIVING UNIT [72] Inventors: Johann 0. Kleinschmidt; Heinz E.

Walter, both of Blankenloch- Buchig; Helmar H. Holl, Karlsruhe, all of Germany [73] Assignee: The Singer Company, New York,

[22] Filed: June 10, 1971 [21] Appl. No.: 151,664

[52] U.S. Cl ..1l2l220 [5l Int. Cl. ..D05b 69/24 [58] Field of Search ..l l2/220, 219 A, 219 R, 67,

[56] References Cited UNITED STATES PATENTS 2,920,257 l/l960 Miles et al ....1 112/219 A X 51 3,698,334 51 Oct. 17, 1972 2,970,557 I 2/1961 Schwab et al ..1 12/219 A 3,367,296 2/l968 Hamuff ..l l2/2l9 A 3,482,538 l2/l969 Hayashi et al. ..1 12/219 A Primary Examiner-J1. Hampton Hunter Attorney--Marshall J. Breen, Chester A. Williams, Jr. and Robert E. Smith [57] ABSTRACT A direct drive unit for a sewing machine applied on the sewing machine frame co-axially of the sewing machine main shaft including a device for producing signals responsive to discrete positions of the sewing machine main shaft. The position signaling device is capable of indicating a plurality of different angular positions of the sewing machine main shaft, which positions may be selected simply by turning frictionally restrained arms accessibly located on the free extremity of the drive unit into the angular positions for which signals are desired.

5 Claims, 5 Drawing [Figures PATENTEDHBT 11 1912 I 3698,1334 SHEET 1 OF 2 INVENTORS F g 2 Johann OH Kleinschmidt, Helnz Emll Walter,

Helmor Heinz Holl WITNESS: I X Z @45 w {Mada-40% ATTORNEY POSITION SIGNALING DEVICES FOR SEWING MACHINE DRIVING UNIT BACKGROUND OF THE INVENTION Driving units for sewing machines are known which require signals responsive to discrete positions of the sewing machine main shaft, as for instance, wherein it is desired that the driving unit stop the sewing machine in a predetermined needle position, or wherein an an- 1 cillary mechanism such as a thread trimmer is required to be operated only in a discrete position of the sewing machine main shaft. Prior position signaling devices, however, have not been entirely satisfactory in that they have been complicated and expensive, have provided only very limited ranges of adjustment, and have required the use of tools and in many cases calibration equipment in order to effect a change or adjustment of the discrete main shaft position to be signaled.

BRIEF DESCRIPTION OF THE INVENTION It is an object of this invention to provide a position signaling device for a sewing machine driving unit which is located and arranged for ready adjustment of the discrete angular positions of the sewing machine main shaft which are required to be signaled. The object of this invention is attained by a signaling device located at the free extremity of a direct driving unit carried co-axially of a sewing machine main shaft and comprising an element carried for rotation with the main shaft and capable, upon traversing a discrete angular position, of generating a signal. A frictional coupling secures the rotating element relatively to the main shaft so that the angular position of the rotating element which bears a direct relationship to the angular main shaft position to be signaled, may be changed simply be physically repositioning the rotating element angularly about the main shaft axis.

DESCRIPTION OF THE DRAWINGS With the above and additional objects and advantages in view, this invention will now be described with reference to the accompanying drawings of a preferred embodiment in which:

FIG. 1 is a front elevational view of a sewing machine showing a direct driving unit thereon having this invention applied thereto,

FIG. 2 is an enlarged horizontal cross-sectional view of the sewing machine driving unit taken substantially along line 2--2 of FIG. 1,

FIG. 3 is an exploded perspective view of the posi tion signaling device of this invention,

FIG. 4 is an end elevational view of the free extremity of the driving unit with the end cover plate removed to expose the position signaling device, and

FIG. 5 is an enlarged cross-sectional view taken substantially along line 5--5 of FIG. 4 showing the frictional connection between the rotating arms of the position signaling device and the motor shaft.

Referring to the drawings, FIG. 1 illustrates a conventional sewing machine including a frame with a work supporting bed 11, a standard 12 rising from the bed and abracket arm 13 extending from the standard and overhanging the bed. The sewing machine is illustrated as supported on a power table 14. Thesewing machine is equipped with stitch forming instrumentalities of which the needle 15 is illustrated in FIG. 1, which stitch forming instrumentalities are actuated from a main shaft 16 journaled in the bracket arm 13 of the sewing machine frame. The operative connections between the main shaft and the needle and other stitch forming instrumentalities may take any conventional form.

As illustrated in FIG. 1 a sewing machine direct driv- 0 ing unit, indicated generally at 20, is carried on the the power table, and the wiring harness may include control conduits as well as conductors for a supply to the driving unit.

With reference to FIG. 2 of the drawings, the sewing machine frame at the juncture of the bracket arm 12 and standard 13 is formed with a seat 30 for supporting the driving unit 20. The sewing machine main shaft 16 carries a coupling member 32 which is secured to the sewing machine main shaft by a set screw 34 and by a headed screw 35. The free extremity of the coupling member 32 is formed of a plurality of spaced axially extending fingers 36 by which a driving connection with an electric motor is made, as will be described hereinbelow.

Secured on the seat 30 on the sewing machine frame by cap screws 42 is a supporting casing 41 having a bell-shaped outer flange 44 formed with a motor accommodating seat 45 and with clearance holes 46 for fastening screws 47 by which an electric motor may be fastened thereto.

Secured, as by set screws 50, to the coupling member 32 onthe main shaft 16 of the sewing machine is a handwheel 52. The handwheel is. formed with a continuous rim 53 which is disposed within a circular cavity 54 inside the supporting casing '41. As shown in FIG. 1, the supporting casing 41 is cut away as at 55 at the top portion thereof to expose a segment of the handwheel rim for ready access by the sewing machine operator.

Secured on the motor seat 45 of the supporting casing is an electric motor, indicated generally at 70, and including a cylindrical housing 71 fitted at each end with circular end plates 72 each secured by bolts 73 to provide a substantially airtight compartment 74. Within the airtight compartment a motor shaft 75 is journaled in bearings 76 in the end plates 72. An armature in the form of a disc 77 is made fast on the motor shaft within the airtight compartment and rotates therein relatively to a plurality of permanent magnets 78 supported on the end plates 72. Brushes 79 are also supported within theairtight motor compartment to contact electric windings which may be printed or otherwise provided on the armature disc to provide a low inertia electric motor of the type which is disclosed and described in greater detail in US. Pat. No. 2,970,238, Jan. 31, 1961 of R. L. Swiggett to which reference may be had.

Exteriorly of one end plate 72 of the electric motor 70 and within the supporting casing 41, a brake disc with a surface 91 of high friction material is secured to power the motor shaft 75. Axially shiftable on guide pins 92 secured in the end plate 72 of the electric motor is a brake shoe 93 which is preferably constructed as an ele'ctro-magnet which when energized will be drawn into braking engagement with the friction surface 91 on the brake disc 90. Coil springs 94 on the guide pins 92 serve to urge the brake shoe 93 out of braking engagement when the electro-magnet is deenergized.

Within the supporting casing 41 the electric motor shaft 75 carries a coupling member 100 which is preferably shaped in a fashion similar to that of the coupling member 32 on the sewing machine main shaft 16. The coupling member 100 thus includes axial fingers 101 which are arranged in interdigitated relation with the fingers 36 of the coupling member 32 to define a driving connection between the motor shaft and the sewing machine main shaft. As shown in FIG. 4, the interdigitated fingers 36 and 101 occupy only a fraction of the circumference of the coupling members. A disc 102 of heat insulating material such as rubber or the like is interposed between the coupling members 32 and 100 and is formed with radial teeth 103 which extend between the interdigitated fingers 36 and 101 and fill the circumferential space therebetween.

A base member 107 preferably formed of synthetic plastic material is secured to the free extremity of the direct drive unit by the bolts 73 which hold the electric motor housing together. The base member accommodates a group of locating and signaling devices of which the position signaling device of this invention is included. Reception sockets 108 formed on the base member 107 snugly accommodate securing pins 109 carried by a cover member 110. The cover member extends in overlapping relation with an annular flange 111 on the base member 107 and defines an enclosed compartment 112 within which the free extremity 113 of the electric motor shaft 75 extends. Because of the interconnected coupling members 32 and 100, the motor shaft 75 is secured for movement in synchronism with the main drive shaft 16 of the sewing machine. Therefore, any signal which is responsive to a discrete angular position of the motor shaft 75 will also bear the same relationship to the position of the sewing machine drive shaft and to the stitch forming instrumentalities driven thereby, as for instance, the position of the needle 15.

Secured to the main drive shaft within the compartment 112 is an annular tachometer rotor 120, preferably comprising opposed ferrous plates 121 each formed with inturned fingers 122 which are interdigitated. The plates 121 are disposed one at each side of an annular block 123 which is permanently magnetized. The plates and permanent magnet block may be assembled as a unit on a hub member 125 secured, as by a set screw 126, to the motor shaft 75. Secured, as by screws 127, to the base member 107 and motor end plate 72 is a bracket 128 which carries a coil 129 responsive to the passage adjacent thereto of the fingers 122 of the tachometer rotor and provides recurring signals in an electric circuit 130 of which the frequency of the signals is a measure of the speed of rotation of the motor shaft 75.

Carried by a bracket 138, which is secured to the base member 107 by fastening screws 139, are a pair of electrical coils 140, 140. The coils operate independently each to signal an individual angular position of the motor shaft as will be described below, but since each coil is constructed in precisely the same manner the innermost coil will be designated by prime reference characters corresponding to the numbers applied to the outermost coils. Each of the coils 140, 140' are wound on a ferrous core having a ferrous yoke 142, 142' secured to one end and extending about the coil terminating in spaced relationship to the opposite end of the core to concentrate the magnetic field existing adjacent to the coils. The cores 141, 141' are disposed each closely adjacent to the path of motion of one of a pair of permanent magnets 150, 150' each secured as by an adhesive or by a force-fit into a reception opening in one of the rotating arms 151, 151' carried on the hub member of the tachometer rotor. The travel of each of the permanent magnets 150, 150' past the respective electric coils 140, changes the magnetic flux concentration adjacent to the coil and gives rise to a signal in the form of a voltage pulse in the coil and in the circuits 143, 143' leading from the coils 140, 140.

As shown in FIG. 3, the hub member 125 is formed with a radial flange 152 from which a hub extension 153 of reduced diameter extends. Each of the rotating arms 151, 151' is formed with a circular aperture 154, 154' loosely embracing the hub extension 153 so that the rotating arms 151, 151' may be turned freely on the hub extension. A dished spring washer 155, preferably formed with spaced radial spring fingers 156 for increased flexibility, is carried on the hub extension 153 and is maintained in compression urging the rotating arms 151, 151' against the radial hub flange 152 by a split retaining ring 157 which is seated in an annular groove 158 cut in the free extremity of the hub extension 153.

The restraining torque which must be exceeded before either of the rotating arms 151, 151' can be shifted angularly relatively to the motor shaft 75 is a function of the normal force exerted by the dished washer 155 urging the rotating arms against the radial hub flange 152. If the restraining torque is higher than the maximum torque which is developed during acceleration of the driving unit by the inertia of the rotating arms, the rotating arms will not shift angular position during operation of the driving unit. Preferably, therefore, the dished washer is designed so as to be compressed by the split retaining ring 157 to such a degree that the force exerted and the restraining torque which is developed in response thereto is sufficient to prevent accidental shift of angular position of the arms 151, 151 but not sufficient to interfere with convenient adjustability of the angular position of the rotating arms by a sewing machine operator while the drive is in stopped condition. When the machine is stopped, the end cover member 110 may be removed and one or both of the rotating arms may be manually shifted relatively to the motor shaft 75. Such selection of the angular position of the rotating arms, and of the members 150, carried thereby, which move relatively to the coils 140, 140' during the machine operation, may be accomplished easily and readily with the sewing machine arm shaft 16 being held in desired angular position by manipulation of the handwheel 52 while the rotating arms 151, 151' are shifted.

Reference is made to the co-pending US. patent application of H.E. Walter Ser. No. 155,082 filed June 21, 1971 which describes in detail a control circuit which utilizes the sewing machine position responsive signal pulses generated by the electrical coils 140, 140 of this invention. The above referenced co-pending US. patent application describes the control circuit whereby needle positions are signaled by the device of this invention corresponding to needle-up and needledown conditions of the sewing machine for correlating the operation of mechanisms, such as thread trimming mechanisms, to discrete positions of the sewing machine stitch forming instrumentalities for the proper operation thereof. It will be appreciated, however, that the position signaling device of this invention may also be used for providing control pulses functioning to control any other sewing machine operations which require correlation of the sewing machine position with the operation of ancillary devices.

Having set forth the nature of this invention, what is claimed herein is:

l. A position-signaling device for the actuating mechanism of a sewing machine having a frame and a main drive shaft journaled in said frame, said positionsignaling device comprising a stationary signal generating member secured in a fixed position relatively to said sewing machine frame, a movable member adapted to render said signal generating member effective in response to passage of said movable member closely adjacent thereto, means supporting said movable member for rotation in a path traversing closely adjacent to said stationary signal generating member, and a friction coupling drivingly interconnecting said movable member with said sewing machine main drive shaft, said friction coupling being such as to require for slippage of said movable member relatively to said sewing machine main drive shaft a torque which is greater than the maximum torque generated by the inertia of said movable arm during acceleration of said sewing machine main drive shaft.

2. A position-signaling device as set forth in claim 1 in which a hub member drivingly interconnected with said sewing machine drive shaft has journaled on it a rotatable arm which carries said movable member for rotation, in which said friction coupling comprises a flange on said hub member against which one side of the rotatable arm abuts, spring means engaging the opposite side of the rotatable arm, and means on said hub member for maintaining said spring means under sufficient tension as to require for slippage of said rotatable arm relatively to said sewing machine main drive shaft a torque which is greater than the maximum torque generated by the inertia of said rotatable arm during acceleration of said sewing machine main drive shaft.

3. A position-signaling device as set forth in claim 1 in which said signal generating means comprises an electrical coil and in which said movable member includes a permanent magnet arranged to induce a voltage signal in said coil upon passage of said member closely adjacent thereto.

4. A position-signaling device for a sewing machine having a frame, a main drive shaft journaled in said frame, and a direct driving unit secured to said sewing machine frame and including an electric motor with a mote r shaft interconnect'e d at one end with said sewing mac ine main drive s a said position-signaling device comprising an arm loosely journaled in an accessible position on the free extremity of said electric motor shaft, signal generating means supported in fixed position relatively to said sewing machine frame adjacent to the path of rotation of said arm for providing a pulse responsive to each movement of said arm through a discrete angular segment of said path of rotation, and a friction coupling between said motor shaft and said arm permitting manual rotary adjustment of said arm on said shaft.

5. A position-signaling device as set forth in claim 4 in which said electric motor shaft of said direct driving unit is supported in substantial axial alignment with said sewing machine drive shaft, in which a handwheel accessible to an operator of the sewing machine is fast on said sewing machine main drive shaft between the sewing machine frame and the electric motor of the direct driving unit, and in which a removable cover is provided for the position-signaling device at the free extremity of the electric motor shaft. 

1. A position-signaling device for the actuating mechanism of a sewing machine having a frame and a main drive shaft journaled in said frame, said position-signaling device comprising a stationary signal generating member secured in a fixed position relatively to said sewing machine frame, a movable member adapted to render said signal generating member effective in response to passage of said movable member closely adjacent thereto, means supporting said movable member for rotatioN in a path traversing closely adjacent to said stationary signal generating member, and a friction coupling drivingly interconnecting said movable member with said sewing machine main drive shaft, said friction coupling being such as to require for slippage of said movable member relatively to said sewing machine main drive shaft a torque which is greater than the maximum torque generated by the inertia of said movable arm during acceleration of said sewing machine main drive shaft.
 2. A position-signaling device as set forth in claim 1 in which a hub member drivingly interconnected with said sewing machine drive shaft has journaled on it a rotatable arm which carries said movable member for rotation, in which said friction coupling comprises a flange on said hub member against which one side of the rotatable arm abuts, spring means engaging the opposite side of the rotatable arm, and means on said hub member for maintaining said spring means under sufficient tension as to require for slippage of said rotatable arm relatively to said sewing machine main drive shaft a torque which is greater than the maximum torque generated by the inertia of said rotatable arm during acceleration of said sewing machine main drive shaft.
 3. A position-signaling device as set forth in claim 1 in which said signal generating means comprises an electrical coil and in which said movable member includes a permanent magnet arranged to induce a voltage signal in said coil upon passage of said member closely adjacent thereto.
 4. A position-signaling device for a sewing machine having a frame, a main drive shaft journaled in said frame, and a direct driving unit secured to said sewing machine frame and including an electric motor with a motor shaft interconnected at one end with said sewing machine main drive shaft, said position-signaling device comprising an arm loosely journaled in an accessible position on the free extremity of said electric motor shaft, signal generating means supported in fixed position relatively to said sewing machine frame adjacent to the path of rotation of said arm for providing a pulse responsive to each movement of said arm through a discrete angular segment of said path of rotation, and a friction coupling between said motor shaft and said arm permitting manual rotary adjustment of said arm on said shaft.
 5. A position-signaling device as set forth in claim 4 in which said electric motor shaft of said direct driving unit is supported in substantial axial alignment with said sewing machine drive shaft, in which a handwheel accessible to an operator of the sewing machine is fast on said sewing machine main drive shaft between the sewing machine frame and the electric motor of the direct driving unit, and in which a removable cover is provided for the position-signaling device at the free extremity of the electric motor shaft. 